Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$146.88	4.792%	$153.9185	$153.92	$153.90	$153.90
Purchase #2	$48.33	9.506%	$52.9242	$52.92	$52.90	$52.90
Purchase #3	$160.33	4.696%	$167.8591	$167.86	$167.85	$167.90
Purchase #4	$72.64	3.203%	$74.9667	$74.97	$74.95	$75.00
Purchase #5	$81.58	5.472%	$86.0441	$86.04	$86.05	$86.00
Purchase #6	$60.97	10.654%	$67.4657	$67.47	$67.45	$67.50
Purchase #7	$168.84	12.187%	$189.4165	$189.42	$189.40	$189.40
7 purchase totals =	$739.57		$792.5948	$792.60	$792.50	$792.60